Plön (Ploen) is a Kreis (district) in the eastern part of Schleswig-Holstein, Germany. It extends from the coast of the Baltic Sea to the western part of the region called "Holsteinische Schweiz" (Holsatian Switzerland). Area 1081 km², population 131,400 (2002). The district's capital is the city of Plön.
The inland part of this small district is covered with lakes. The Großer Plöner See ("Great Lake Ploen", 29 km²) and the Selenter See ("Lake Selent", 22 km²) are the largest lakes in Schleswig-Holstein. The lakeland and the adjoining parts of the neighbour district Ostholstein constitute the region called Holsatian Switzerland, since this is a very hilly countryside. However, the hills are not higher than 150 m. North of the lakeland there is the Probstei, a countryside at the coast of the Baltic Sea.
Towns in the district of Plön: Plön, Preetz, Lütjenburg.